1. Field of the Invention
This invention relates to a switch in which a movable contact is connected to and disconnected from a stationary contact by a rocking action of an actuator.
2. Statement of the Prior Art
Heretofore, a kind of such a switch is disclosed, for example, in Japanese Utility Model Publication No. 35150/1985.
The prior switch comprises a switch body, a switch handle, a base plate on the backside of the handle, a resistor for protection of limited flow, an indication lamp, a pattern face having two ways of conductive layer formed on the backside of the base plate, a load terminal device, an indication circuit terminal device, and a power source terminal device. The load terminal device and the indication circuit terminal device are electrically connected through a contact spring to the base plate. A switching means is disposed among the load terminal device, the indication circuit terminal device, and the power source. The connection between the devices is turned on and off by operation of the handle to electrically connect a serial circuit comprising the resistor for protection of limited flow and the indication lamp.
In the prior switch, a contact element of the switch means and a contact plate connected to a terminal plate are made of a copper alloy sheet. When the contact element and plate is heated above a given temperature by sparks therebetween, a thin layer of copper peroxide is generated on the surface of the contact element and plate to increase the electric resistance and this results in generation of a further high temperature.
In particular, when the prior switch is used for a load of a high power factor type of a fluorescent lamp, an over-current flows on throwing the switch to generate sparks and to melt the contacts. Finally, it becomes impossible to disconnect the contacts.
In order to overcome such problem, it may be contemplated to make either contact element or contact plate with a high conductive noble metal such as silver. However, since the silver itself is not only precious but also soft, there still remains a problem that contacting portion is readily worn by rocking action of the contact element.
In addition, in the prior switch, a movable frame is bridged between a rotary shaft to be actuated by the switch handle and the terminal plate to be pivoted by the switch body, and the rotary shaft activates the movable frame. This construction makes the assembling work very complicated and requires great skill.